The present invention relates to a power generation apparatus for an electric hybrid automobile having a.c. generators which are driven by an internal combustion engine and serve as a power source for an induction motor for cruising.
FIG. 3 is a diagram showing a conventional power generation and moving mechanism of an electric hybrid automobile provided with a power generation apparatus. In FIG. 3, reference numeral 1 designates an internal combustion engine, numeral 2 designates an a.c. generator driven by the internal combustion engine 2 through a belt-connection means 3 at a rotation speed of three times as fast as a rotation speed of the engine, numeral 4 designates a rectifier for rectifying an a.c. voltage of the a.c. generator 2 into a d.c. voltage, numeral 5 designates a battery as an auxiliary d.c. power source, which is charged with an output voltage of the rectifier 4, and numeral 6 designates a control device which controls an exciting current in the a.c. generator by means of a voltage regulator by detecting an output voltage of the rectifier 4 to thereby effect voltage regulation, and converts a d.c. voltage from the rectifier 4 into an a.c. voltage by means of a stationary type inverter. The control device 6 also changes the frequency of the a.c. voltage. Numeral 7 designates an induction motor which receives the a.c. voltage under the control of the control device 6. The rotation speed of the induction motor is controlled by the change of the frequency of the a.c. voltage by the control device 6. Numeral 8 designates a differential gear to which the rotational force of the induction motor 7 is transmitted. The differential gear 8 rotates the wheels 10 through an axle 9.
The internal combustion engine has an operating zone at or near 3,000 rpm as a rated engine speed which provides the most effective fuel consumption efficiency. In that operating zone, the operation for a substantially constant rotation speed is conducted. The internal combustion engine 1 has another operating zone at or near 4,000 rpm which is used when the maximum speed or the maximum acceleration is necessary for the automobile, and another operating zone in a range of 1,000 to 1,500 rpm when the automobile is operated with the battery 5 fully charged, or when the automobile is stopped for a long time. Accordingly, for the a.c. generator 2 used for a conventional automobile, there is a requirement that the output current characteristics corresponding to the engine rotation speed should satisfy values at three points I.sub.1, I.sub.2 and I.sub.3 of an output current from of the rectifier which are indicated by X marks in FIG. 4. In order to satisfy the above-mentioned output current characteristics, the size of the a.c. generator 2 is necessarily large. The output voltage of the rectifier 4 is, for instance, 280 V and the voltage of the battery 5 is, for instance, 240 V.
The conventional power generation apparatus for an electric hybrid automobile has the following disadvantages. Since the single a.c. generator 2 to be driven has to bear the supply of power so as to cover a rotation speed range from a rotation speed the idling of the combustion engine 1 to a rotation speed which corresponds to the maximum power of the automobile, the size of the generator 2 is necessarily large, and the efficiency of the operation of the engine is low at the rated engine speed at which a high efficiency is necessary (usually, the operation of the engine at the rated engine speed is most frequently used). Further, there is difficulty in mounting and arranging the large-sized generator 2 on the internal combustion engine 1. Further, since the size of the generator 2 is large, a fairly large-sized belt connection means 3 which connects the a.c. generator 2 to the internal combustion engine 1 is required.